The present invention relates to universal joints, and more particularly to an improved journal and bushing design.
Universal joints of various types have been known since antiquity, and take many forms. Perhaps the most widely-used form of universal joint is the cross-type or Hooke's joint which is in common usage for Hotchkiss drive vehicles, and is further used for industrial drives, power takeoffs, and the like. This form of universal joint ordinarily comprises a pair of U-shaped yokes, one on a driving shaft and one upon the driven shaft. A cross-shaped trunnion having four journals, usually oriented 90.degree. apart, is used to couple the yokes. Each yoke receives a pair of opposed journals in appropriate bearings, bushings, or the like.
Ordinarily the journals of the trunnion are received in cup-shaped bushings. The sides of the journals may bear directly upon the walls of the bushing, in the manner of a plain bearing. Needle bearings or sleeves of a dissimilar material may be used to further decrease the friction between the journal and the bushing. The bushings are located in their respective yokes by means of clamps, interference fits, C-shaped spring washers, welding or other appropriate means.
Under some conditions of operation, substantial end thrust is generated whereby the axial ends of the journals bear against the inner surfaces of the bushing ends. While end thrust is ordinarily not great, under some circumstances it is sufficient to cause galling and/or heating of the journal surfaces. The heating is detrimental to the entire bearing system inasmuch as it may destroy lubricant retained within the bushing, and in extreme cases can soften or draw the temper from the hardened surfaces of the journal or bushing. Bits of metal which have been abraded from the thus-deteriorated bearing system further accelerate the wear and degeneration of the universal joint and the joint soon fails.
Although this problem has been recognized for some time and efforts made to overcome it, to date no simple, inexpensive design has been advanced. Some replacement-type universal joint trunnions for automobiles and light trucks have been provided with axial passages through which grease can be pumped to the bearings. Alternatively, thrust members of hardened steel, bronze or glass-filled nylon have been disposed between the ends of trunnion journals and the bottoms of the bushings which receive them. Both of these approaches, however, necessitate additional machining and/or parts and thus add to the complexity and expense of the univeral joint assembly. It will therefore be appreciated that it would be highly beneficial to produce an inexpensive universal joint assembly which exhibits superior resistance to deterioration resulting from the end thrust of trunnion journals.
It is therefore an object of the present invention to provide a universal joint assembly which is capable of withstanding greater end thrust than previous designs of comparable cost and simplicity.
Another object of the invention is to provide a method for forming an improved universal joint pivot assembly.
Another object is to provide an enclosed trunnion bearing which retains sufficient lubricant to last for its anticipated service life.